1. Field of the Invention
This invention relates to a pressure regulator of the liquefied-gas fuel system for internal combustion engines.
2. Prior Art
In conventional fuel feed systems of this character, the fuel from a liquefied-petroleum-gas (hereinafter called "LPG") tank is vaporized with pressure reduction to about atmospheric by a pressure regulator, and the fuel in a gaseous state is admitted to the venturi throat of a carburetor where it is mixed with suction air before being delivered to the engine cylinders.
The existing LPG supplying apparatus have disadvantages. Dust and other impurites carried by the suction air tend to clog the filter of the air cleaner and, when partially clogged, the filter will provide a greater resistance to the air passing therethrough and will thereby increase the negative pressure in the venturi of the carburetor. Such an increased negative pressure causes the venturi to draw in more LPG and less air, with the result that the engine is supplied with an overrich fuel. In addition, because the gas reduced in pressure to about atmospheric by the pressure regulator is delivered to the carburetor, the pressure is often too low for the gas to mix well with air in the venturi, and the air-fuel ratio is likely to be affected by the intake pulsation of the engine. Furthermore, the ordinary fuel supplying apparatus tend to produce too lean fuel mixtures because of their inability to respond aptly to the quick changes in the quantity of suction air during the engine acceleration.
An LPG supplying apparatus capable of eliminating the foregoing disadvantages of the conventional systems and of supplying an engine with a gaseous mixture at a proper air-fuel ratio has already been proposed. (Japanese Patent Application No. 11416/73)
In the proposed apparatus, LPG is gasified by a pressure regulator and, in an adequate proportion to the suction air, metered into the carburetor. The apparatus permits the use of a relatively high pressure, e.g. at 0.2 - 0.6 kg/cm.sup.2, and hence satisfactory mixing of suction air and gasified fuel.
The above-mentioned fuel supplying apparatus for internal combustion engines includes an air valve turnably supported by a shaft above the throttle valve in the carburetor, and is equipped with a controller for opening and closing the air valve under controlled conditions. The controller has a housing and a diaphragm that partitions the space inside the housing into two chambers, one of which is communicated with the space above the air valve in the carburetor, and the other chamber with the space between the air valve and throttle valve in the carburetor. Inside the latter chamber is disposed a spring capable of maintaining the diaphragm in a balanced state against the differential between the pressures exerted on the opposite sides of the diaphragm. The air valve and diaphragm are operatively connected by linkage.
However, the prior art apparatus is designed for operation with a preset air-fuel ratio and cannot meet any engine requirement for fuel with different ratios. In other words, the apparatus once set for ordinary or part-load operation would no longer suit for operation at heavier loads, for example at full load. Usually, with internal combustion engines that burn liquefied gases, the air-fuel ratio of the mixture is preferably 15:1 for light-load operation and 12:1 for full-load operation. Thus, if the air-fuel ratio can be automatically switched during the engine operation from the light-load to the full-load condition and vice versa, the afore-described liquefied fuel supplying apparatus would be able to maintain the preset air-fuel ratio regardless of the amount of suction air, and it should be clear that a technical progress would then be achieved over the original proposal.